Jesse McCartney was 21 in Alvin and the Chipmunks: The Squeakquel when he played the character 'Theodore (voice)'.
That was over 14 years ago in 2009.
Today he is 37, and has starred in 28 movies in total, 17 of those since Alvin and the Chipmunks: The Squeakquel was released.
In Alvin and the Chipmunks: The Squeakquel, I think Jesse McCartney looks: